1. Field of Invention
The present invention relates to a flat thin dynamic speaker, and more particularly to a flat thin dynamic speaker with a novel arrangement of components that yields a large radiating surface area and high output levels compared to conventional dynamic speakers of the same thickness and footprint by having the magnetic circuit at the same level as the suspension means.
2. Description of Related Arts
For many products containing speakers such as flat screen television receivers, cell phones, and portable computers, it is desirable to use speakers as flat and thin as possible and often in shapes other than round or ellipse so as not to limit the designer's options for the design and appearance of the products.
The major elements of a conventional dynamic speaker are schematically illustrated in FIG. 1. This type of speaker consists of four major components: a frame 4′, upon which the structure rests; a radiating means 1′, such as a piece of paper or plastic, or a metal cone or dome which couples with the speaker to a transmission medium such as air or water; a flexible suspension means 2′ to mechanically attaching the radiating means and any other moving parts to the frame 4′ in such a way as to allow motion of the radiating means 1 in one axis while constraining motion in the other two axes and at the same time providing a restoring force along the Z-axis, and a driving means 3′, or motor, which provides a force to move the radiating means 1′ in response to a driving voltage, which is analogous to the desired acoustic output of the speaker assembly.
The physical size and mass of each of the components are usually optimized for particular applications, such as those used to reproduce particular ranges of frequencies and power (sound pressure) levels, or to couple to various acoustic transmission media such as air and water. The physical size of the components necessary for a particular application constrains the range of sizes of the speaker assembly, and the conventional arrangement of components makes it difficult to design well performing speakers in shapes other than ellipses and circles.
The conventional approach to making speaker thinner is schematically illustrated in FIG. 2 and graphically illustrated in FIG. 3A to 3C. In this case, the flexible suspension means 2′ is incorporated into the periphery of the radiating surface 1′. This approach allows for a lower profile, but it has several disadvantages that hurt performance.
For good performance, the radiating surface 1′ needs to be relatively stiff, yet the portion of the radiating surface 1′ that acts as the flexible suspension means 2′ needs to be flexible. A common means of mitigating the desultory effects of these conflicting requirements is to compromise the stiffness of the material and to corrugate the region that acts as the flexible suspension means. This allows the designer of the speaker to make tradeoffs among the stiffness of the radiating means, the flexibility of the flexible suspension means, the thickness of the speaker and performance.
The conventional thin speaker approach also trades away some of the available surface area available for a given size radiating means to radiate power to make room for the flexible suspension means and also reduces the total available displacement along the Z-axis for lacking additional suspension.
Reducing the total available displacement along the Z-axis results in a lower maximum power output for a given radiating means 1′ surface area. The reduced surface area available further reduces the maximum achievable acoustical output power.
The conventional thin speaker approach trades away performance to reduce thickness and is unsatisfactory.